Inclusion Criteria:

• Give informed consent
• Be able to understand the nature of the study, agree to comply with study requirements, report regularly for scheduled visits, and communicate with study personnel about adverse events and concomitant medication use
• Be between 18 and 60 years old
• Meet DSM-IV criteria for both current cocaine and alcohol dependence
• Be in acceptable health based on physical exam, lab tests, and EKG
• Have a stable living situation and the availability of at least two locators
• Be able to read and write English at the 6th grade level
• Provide a least one cocaine positive urine during intake
• If female, must agree to use contraception

Exclusion Criteria:

• History of evidence of a medical condition that would expose them to an undue risk or interfere with assessments during the course of the trial, including but not limited to hepatic, renal, respiratory, cardiovascular, endocrine, or neurologic disease as determined by the clinical judgment of the research team
• Medical condition that is contraindicated with opioid antagonists or necessitates opiate medication
• Abnormal liver function test results (both ALT and AST >3x upper limit normal or either >5x upper limit normal)
• Currently in treatment or have received treatment in the past six months for substance abuse or another psychiatric condition
• Evidence of a Axis I disorder that will interfere with the course of the trial, including but not limited to current Major Depressive Disorder, Bipolar Disorder, Panic Disorder, Schizophrenia, Bulimia nervosa or Anorexia, and Post-traumatic stress disorder as determined by the clinical judgment of the research team
• Participating in 12 step meetings more than twice weekly
• Opiate abuse or dependence in the last five years or used opiates, barbiturates, benzodiazepines in the last thirty days
• Current dependence on any psychoactive disorder other than nicotine
• Impending incarceration
• Condition of probation or parole requiring reports of drug use to officers of the court
• Women of child bearing potential must not be pregnant/lactating or unwilling to use an acceptable contraceptive method
• Plans to move from the Houston area within the next three months